February 10, 2021
Civil Engineering is a complex and interesting field. When it comes to the specific arena of geotechnical engineering, monitoring, and Instrumentation, there are various sensors that are employed to get the work done. In this article, we are going to discuss data loggers, it’s various types, and how they are used in the geotechnical field
Civil Engineering is a complex and interesting field. When it comes to the specific arena of geotechnical engineering, monitoring, and Instrumentation, there are various sensors that are employed to get the work done. In this article, we are going to discuss data loggers, it’s various types, and how they are used in the geotechnical field.
To put it simply, data loggers are simply the devices that are interfaced with several other instruments or sensors to log data in real-time. While these devices are used in various fields, their application in the geotechnical field is of utter importance.
Large construction sites or even civil engineering structures require continuous monitoring to maintain its health. For the overall safety of the structure and those living within the zone of influence, geotechnical monitoring plays a crucial role. A variety of monitoring instruments and sensors are installed at these places to record parameters such as humidity, pressure, deformity etc.
As these sensors do their job, the Data loggers are responsible for collecting and recording data from the installed sensors for an assigned duration, at predefined intervals, without any physical/human intervention.
Let’s take a look at the data loggers in detail along with their types, working principle, and more.
A data logger is usually a compact, battery-powered device and carries a digital processor. Data loggers are interfaced with geotechnical sensors to log data from them automatically.
Once programmed, commissioned and activated, the data logger can be left unattended to measure and record data from sensors. It allows for regular structural health monitoring for minimising risk.
Let’s take a look at the data logger working principle.
Data loggers are connected to the sensors through cables. A single data logger can be interfaced with multiple sensors depending upon the availability of the channels.
After programming, these data recorders are left unattended to record data from the sensors and store it in its internal non-volatile memory. The device can log multiple parameters from the sensors along with current time, date, and battery voltage.
The data stored in the memory of data loggers is transmittable through telemetry or using a laptop/PC.
Now that you’re aware of what is a Data Logger and its working principle, let’s take a look at its applications.
| Read More: Data Loggers: What is it, Types, Applications & How it Works? |
Data loggers have a wide range of applications, especially in the geotechnical field. They are used for the following purposes:
We have already defined data loggers and explained its application in the geotechnical field. Let’s now have a look at the types of data loggers.
Bluetooth data recorder is a simple wireless data logger. It measures, records, and transmits data wirelessly to computers/laptops within a specified range say, 30 metres. These data loggers work on Bluetooth connectivity.
USB data loggers record and store the data in their internal memory. The data recorded can be retrieved on a PC or laptop using the USB cable interface. The same USB is used to charge up the data logger.
The web-based data loggers allow for remote data retrieval using Internet, Wi-Fi, or GPRS. Encardio Rite deals with web-based data loggers. The Encardio’s range of data recorders include:
The Encardio Rite’s Model ESDL-30 multi-channel data logger is designed to record data from sensors with SDI-12 interface. Any sensor with an SDI-12 interface can be connected to ESDL-30 e.g. based on vibrating wire, resistance strain gauge or MEMS technology etc.
ESDL-30 is a robust vibrating wire data logger that finds its application in a variety of fields to provide accurate and reliable data. It features a wide operating temperature range, dependable stand-alone operation, low power consumption, compatibility with many telecommunication options, and flexibility to support a variety of measurements as well as control applications. It is of durable construction and very suitable for unattended applications.
ESDL-30 data logger is connectable to a large number of sensors with SDI-12 interface. The data logger is fully compatible with all measurement commands signal as per SDI-12 standard. It can be programmed to take readings from 5 seconds to 168 hours in linear mode.
However, the number of measurements taken per day should be kept minimum to prevent power drain from the batteries.
The SDI-12 serial digital interface requires a three conductor cable to connect the sensors to the data logger. The advantage of the instrument is that only a single 3-conductor cable is required to interconnect all the sensors and the data logger to a serial bus.
SDI-12 is a multi-drop interface that can communicate with multi-parameter sensors. Multi-parameter means that a single sensor may return more than one measurement, like displacement and temperature from vibrating wire displacement sensors.
All the data recorded by the vibrating wire data logger is stored along with the current date, time, and battery voltage in its internal non-volatile memory.
The data logged by the digital data loggers is retrievable at any remote location through a dedicated web-based cloud server. There are a couple of methods to retrieve or transmit data to a distant location:
Telemetry through GSM/GPRS modem
In a location covered by any GSM/GPRS service provider, the data from the automatic data logger can be transmitted remotely to a PC at a central location. The user will need to arrange a data SIM card for each data logger.
Readout/data retrieval using laptop PC
The logged data from the data logger in the field can be directly downloaded to a laptop/PC. Data can be transferred to the central PC or server from the laptop using either a USB pen drive or through the Internet.
Encardio Rite offers a public dedicated cloud-based web monitoring service to its clients for retrieving data from the ESDL-30 data logger. The data retrieved is archived and stored in a SQL database. The same data is represented in the form of tables and graphs for easy understanding.
The information logged can be accessed only by authorised personnel who can log in to their site using the supplied login ID and access password from anywhere in the world.
Watch the video below to know the sensor configuration of ESDL-30 data logger with ESDL-30 UNI application software:
2 x D size 1.5 V Alkaline high power cells, or
12V SMF battery chargeable from AC mains or solar panel
Encardio Rite Model ESCL-12VT Single Channel Data Logger is curated for the collection of data automatically from any vibrating wire sensor equipped with an integral thermistor. The telemetry option allows you to send the data to cloud/private server with the help of an in-built GPRS/GSM modem at specified intervals. The interval in between can be as quick as 5 minutes.
The combination of automatic collection and wireless transmission of data assists in significantly diminishing the field costs and helps to provide easy access to near real-time data with set alarms and warning signs.
The Single Channel Data Logger is equipped with a capability of two way communication. This further attempts to lower down the field costs as it provides remote access to configure, receive system status update, and carry out maintenance or diagnostics and preventive actions from the office itself. You’re no longer obliged to visit the site after installation.
Coming to the application of Model ESCL-12VT Data Logger, it is found in many areas of the geotechnical field. It helps to impart accurate and reliable information from vibrating wire sensors along with a wide operating temperature range, dependable standalone operation, and low power consumption. It is also very compatible with many telecommunication options and provides enough flexibility to support a variety of measurement and control applications. The on board 5-pin connector is used for rapid sensor connection, whereas the durable construction makes it well-suited for unattended applications.
Temperature: Thermistor type, Dale 1C3001-B3, temperature range -40 to +100°C
Temperature: ± 0.1°C
(excluding sensor inaccuracy)
Real time clock: ± 1 minute/month
Temperature: ± 0.01°C
Real time clock: 1 second
>3 Years with 3 V Alkaline Battery (with 4 scans/day and 1 upload/day)
The Model ESCL-10VT single channel vibrating wire data logger is designed to monitor a single vibrating wire sensor (including temperature) such as a piezometer, pressure sensor, and crack meter or displacement transducer. It can make data logging rain level quite easy.
The single channel data logger can additionally monitor barometric pressure and has provision to monitor rainfall using a tipping bucket rain gauge. The barometric data logger has Windows-based application software with features that allow the user to set the sensor calibration coefficients, recording intervals, data logger or borehole code (identification tag numbers), sensor serial number, real-time clock time etc. conveniently.
The user can monitor readings and GPRS signal strength for diagnostic purposes. The user can also start or stop the scan and can manage data files, download data from the data logger, perform data correction, and save the data files.
The most common use of the ESCL-10VT data logger is for online monitoring of water level. The water level/table is monitored by using a high accuracy fluid pressure sensor installed at a depth below the minimum expected water level.
A thermistor is incorporated in the sensor for measurement of water temperature. The sensor is connected to the data logger for automatic collection of data. The recorded data is then transferred by the data logger to a remote server/cloud server.
The groundwater data logger transfer device has an inbuilt barometric sensor which allows the water level to be corrected for barometric pressure variation. The use of a barometric pressure sensor eliminates the apparent variation in water level due to variation in atmospheric pressure. The system provides the correct value of water level along with barometric pressure and temperature to the user.
Water level/table reading from a pressure sensor is dependent on the specific gravity of water at that location. For example, if the specific gravity is 1.08, the pressure sensor will give an 8 % higher output as compared to normal water which has a specific gravity 1.0.
In coastal areas or in water with high dissolved solid content, the specific gravity of water will have a value higher than 1.0. The measured value of specific gravity must be entered in the data logger so that it can provide the corrected value of water level/table.
The water pressure data loggers measure the output from the absolute and barometric pressure sensors as well as temperature and calculate the pressure in terms of water column after correcting for the measured barometric pressure and water density. The data is stored, together with the current date, time and battery voltage, as a data record in internal non-volatile memory of the data logger.
ESCL-10VT single channel data logger has provision to attach model ERG-200/ERG-201 rain gage for simultaneous monitoring of rainfall along with the water level/table monitoring. This helps in correlating the water table data with the rainfall data.
The data retrieval and transmission process of the ESCL-10VT is similar to that of the Model ESDL-30 data logger.
Cylindrical: Corrosion resistant stainless steel, AISI grade 316L.
That was all about the types of data loggers and their application in the geotechnical field. If you have any queries or suggestions, feel free to drop us a comment below.
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